In a move that coincidentally sees two App Store rebels join forces, music streaming service, Grooveshark, has added support for Flattr, the social micro-payments offering. The new integration means that users of both Grooveshark and Flattr (which we’ve previously likened to a ‘Like button but with cash‘) can easily reward their favourite artists, tip jar-style, providing another way for those artists to get paid for their music uploaded to Grooveshark. Both services have at one time or another fallen foul of Apple’s App Store policies (see below).

The new partnership between the two companies isn’t without a few caveats, however, and it’s questionable whether this is finally — finally — the breakthrough that Flattr has been looking for to prove that its idiosyncratic payments model actually has legs. Meanwhile, for musicians and bands whose music is uploaded to Grooveshark, sometimes without permission, tip jar-style donations as a means of getting paid probably isn’t quite what they had in mind. They’ll also be required to register with Flattr to claim any donations rather than Grooveshark handling the distribution of funds.

The new Flattr integration follows a major re-design of Grooveshark and sees the Flattr button added to all of the 250,000+ artist pages on the music streaming site, which claims 30 million users. That’s probably a lot closer to the exposure that Flattr was hoping for when it signed a similar, albeit limited, partnership with the number two video sharing site, Dailymotion. We’re hearing from sources that, just as predicted, this indeed didn’t pan out to be quite the ‘stress test’ that it was talked up to be at the time, and from Flattr’s vantage point, the results have been disappointing. Certainly, in comparison, the arrangement with Grooveshark looks more promising — although we remain unconvinced that Flattr has the social micropayments nut anything like cracked.

A quick reminder of how the service works: A user decides how much they want to spend per month, then, whenever they see a Flattr button on the web or mobile, they click to donate. At the end of the month, Flattr counts up all of a user’s clicks and distributes the funds evenly — taking a cut along the way.

The purely voluntary and pooled nature of the service is undoubtedly left-field, and when you consider who founded the social micro-payments site — Peter Sunde, co-founder and (now) ex-spokesperson of the Pirate Bay, no less — things get even more intriguing.

The Pirate Bay, of course, has long been at war with the record labels, and it’s noteworthy that Grooveshark has found itself in choppy waters with the music industry, too, relying on the ‘safe harbour’ protection of the DMCA to stay afloat. That’s because, unlike many other music streaming services, users can upload content to Grooveshark, simply by ticking the box saying that they have permission to do so.

This has meant Grooveshark and the record labels playing a cat and mouse game of DMCA take-down notices, the same game that YouTube played for years, and one that has seen Grooveshark rejected by Apple’s iOS App Store and on Google Play, too.

Interestingly, Apple doesn’t seem too fond of Flattr’s tip jar-style micro-payments model either, and at least one iOS app that integrated Flattr has been similarly rejected. (Although others have been accepted, so this could simply be a one-off — it’s not like the iOS App Store isn’t a moving target, anyway).

Regardless of what we think about the viability of Flattr’s social micro-payments model or Grooveshark’s reliance on safe harbour, as we move away from the open web, it’s worth pausing for thought to consider how the big app store providers, such as Apple and Google, are in danger of becoming the gatekeepers of innovation — if that hasn’t happened already.